Lipid-lowering drugs and risk of new-onset diabetes: a cohort study using Japanese healthcare data linked to clinical data for health screening

Objective To investigate whether lipid-lowering drugs are associated with new-onset diabetes after adjusting for baseline clinical risk factors for diabetes. Design A retrospective cohort study. Setting Japanese employees of large corporations and their dependents using health insurance claims data linked to clinical and laboratory data for annual health screenings. Participants All persons aged 20 to 74 years with dyslipidaemia between 1 January 2005 and 31 March 2011. We defined the index date as the first date when the person met the criteria for dyslipidaemia. Persons were excluded if they had lipid-lowering drugs, or had a diagnosis, a treatment or a laboratory test result (haemoglobin A1c ≥6.5% or fasting blood glucose ≥126 mg/dL) indicating diabetes during the 6-month period before the index date. Main outcome measures New-onset diabetes. Results We identified 68 620 persons with dyslipidaemia. During the mean follow-up period of 1.96 years, 3674 persons started treatment with a lipid-lowering drug: 979 with a low potency statin, 2208 with a high potency statin and 487 with a fibrate. Of 3674 new users of a lipid-lowering drug, 3621 had a period of non-use of any lipid-lowering drugs before starting a lipid-lowering drug. Among statin users, the incidence rate of new-onset diabetes was 124.6 per 1000 person-years compared with 22.6 per 1000 person-years in non-users. After adjusting for confounding factors including clinical data in health screening using Cox proportional hazards models, the HR was 1.91 (95% CI 1.38 to 2.64) for low potency statins and 2.61 (2.11 to 3.23) for high potency statins. Conclusion The use of statins was associated with a 1.9-fold to 2.6-fold increase in the risk of new-onset diabetes in a Japanese population of working age, despite adjusting for clinical risk factors for diabetes.